WASHINGTON — The closed-door “training academy” was aimed at a select group: recent law school graduates who had secured prestigious clerkships with federal judges. It was organized by the Heritage Foundation, a conservative group that has played a leading role in moving the courts to the right, and it had some unusual requirements.

“Generous donors,” the application materials said, were making “a significant financial investment in each and every attendee.” In exchange, the future law clerks would be required to promise to keep the program’s teaching materials secret and pledge not to use what they learned “for any purpose contrary to the mission or interest of the Heritage Foundation.”

The conservative legal movement has made bold moves before, and it has long cultivated law students and young lawyers, partly to ensure a deep bench of potential judicial nominees. The Heritage Foundation, along with the Federalist Society, helped compile the lists of potential Supreme Court nominees from which President Trump chose his two appointees, Justices Neil M. Gorsuch and Brett M. Kavanaugh. The two groups also helped identify many of the scores of Mr. Trump’s appointees to the lower federal courts.

But legal experts said the effort by Heritage to train and influence law clerks raised serious ethical questions and could undermine the duties the clerks have to the justice system and to the judges they will serve.

“Law clerks are not supposed to be part of a cohort of secretly financed and trained partisans of an organization that describes itself on its own web page as ‘the bastion of the American conservative movement,’” said Pamela S. Karlan, a law professor at Stanford. “The idea that clerks will be trained to elevate the Heritage Foundation’s views, or the views of judges handpicked by the foundation, perverts the very idea of a clerkship.”

On Thursday afternoon, a few hours after The New York Times published an online article about the training, Heritage announced that it was suspending the program.

“Heritage is re-evaluating the Federal Clerkship Training Academy,” Greg Scott, a spokesman for the group, said in a statement. “As a result, the program will not go on as scheduled.”

Before the article was published, Breanna Deutsch, a spokeswoman for the group, declined to answer detailed questions about the program, which had been scheduled for early February.

“It’s a private program, and that’s the way we’d like to keep it,” she said in a brief interview Tuesday morning. “Word did leak out a little bit about it, which is fine, but it’s going to remain a private program.”

A few hours later on Tuesday, Heritage deleted the references to donors, secrecy and loyalty from the application materials it had posted on its website. Ms. Deutsch did not respond to a request for an explanation and to other questions about the program. Nor would she disclose the identities of the program’s donors or its faculty, which was said to include several sitting federal appeals court judges and professors “from various prominent law schools.”

Jill Dash, vice president for strategic engagement at the American Constitution Society, which is often described as the Federalist Society’s liberal counterpart, said there was no comparable program aimed at liberal law clerks.

“I am not aware of anything like this on the progressive side,” she said.

According to the application materials, Heritage’s unnamed donors were to pay for travel expenses to Washington, hotel rooms and meals during the three-day program. The curriculum would cover, the materials said, “originalism, textualism, habeas corpus, the Bill of Rights and other substantive legal and practical subject matter.” Originalism and textualism are modes of interpreting the Constitution and statutes that are generally but not exclusively associated with conservatives.

The application called for several short essays. One prompt said, “Please describe your understanding of originalism.” Another said, “Please identify the United States Supreme Court justice (past or present) whose jurisprudential philosophy and approach to judging you agree with most, and explain why.”

It was unclear whether an applicant hostile to originalism, which seeks to interpret the Constitution as it was understood by those who drafted and ratified it, or who named a liberal justice would have been admitted to the program.

Lawrence Baum, a political scientist at Ohio State University, said the program was an extension of other initiatives from the Heritage Foundation and the Federalist Society.

“One hallmark of the conservative legal community since the 1980s has been the efforts of its leaders to identify and nurture promising young lawyers with conservative views who may rise to important positions such as judgeships,” he said. “This academy is a good example of those efforts.”

“The people who are chosen to clerk for federal judges are a talented group, and the application form indicates an interest in identifying and training future clerks who are especially accomplished and who are committed to conceptions of the law that conservatives favor,” he said. “The willingness of conservative groups to invest in the future in this way is one reason that the Federalist Society and the Heritage Foundation could recommend potential Trump nominees to the Supreme Court with confidence that they were deeply rooted in their conservatism.”

The aspects of the program described in the original materials and later deleted from Heritage’s website raised troubling issues, some legal experts said.

Carolyn Shapiro, a professor at Chicago-Kent College of Law, said she was particularly troubled by the requirement that attendees “keep strictly confidential and not distribute to any other person” the materials provided at the program.

“It seems completely inconsistent with being a law clerk to agree to that kind of condition,” she said. “Does that suggest they can’t even talk to their judges about what they learn?”

“I don’t think there’s anything intrinsically odd about an organization that has a point of view holding event to which law clerks or future law clerks are invited,” she said, “but this reads like a kind of indoctrination.”

Decades ago, ideology played at most a minor role in most federal judges’ selection of law clerks. But the emergence of the Federalist Society in the early 1980s helped change that, and these days many Republican appointees to the federal bench hire mostly conservative clerks and Democratic appointees mostly liberal ones.

The question of whether law clerks influence the judges they serve is a subject of longstanding debate, but it is no secret that law clerks routinely draft judicial opinions. A new study to be published in The Journal of Law, Economics & Organization found that law clerks do indeed play a role in judicial decision-making.

“On average, a justice would cast around 4 percent more conservative votes in a term in which she hired her most conservative clerks versus a term in which she hired her most liberal clerks,” said Maya Sen, a political scientist at Harvard and one of the authors of the study. “So shifting the ideology of all Supreme Court clerks in any one direction would be significant, and it would make sense for ideological organizations to target not just Supreme Court law clerks, but also law clerks throughout the judicial hierarchy.”

Professor Sen said the demand for highly qualified conservative candidates for judicial appointments “tends to outstrip supply, particularly as elite law schools and their graduates are becoming increasingly liberal.”

“This makes conservative networks such as the Federalist Society and now, it appears, the Heritage Foundation, very important in terms of nurturing and identifying young conservative legal talent,” she said. “These networks could nurture the next generation of Neil Gorsuches or Brett Kavanaughs.”

A version of this article appears in print on , on Page A1 of the New York edition with the headline: Conservatives Sought to Train Law Clerks Behind Closed Doors. Order Reprints | Today’s Paper | Subscribe